Refrigerating apparatus and method



May 18, 1943 R. E. GOULD REFRIGERATING APPARATUS AND METHOD Filed March 24, 1941 2 Shets$heet 1 INVENTOR y 1943 I R. E. GOULD 2,319,502

REFRIGERATING APPARATUS AND METHOD Filed March 24, 1941 I 2 Sheets-Sheet 2 IN VENTOR.

Mam BY IQQAM*% Patented May 18,1943

G APPARATUS AND METHOD Richard E. Gould, Oakwood, Ohio, assignor to General Motors Corporation, Drgton, Ohio, a

REFRIGERATIN corporation of Delaware Application March 24, 1941, Serial No. 384,816

Claims.

This invention relates to refrigerating apparatus and more particularly to an improved method and apparatus for conditioning air.

In refrigerating systems of the type most commonly used for conditioning the air for a private home or the like, the air to be cooled is circulated in thermal exchange relationship with an evaporator which removes the necessary amount of heat from the air. The heat removed from the air by the evaporator is dissipated through a condenser over which some form of cooling medium such as air or water must be passed. The condenser may be cooled either by means of air flowing thereover or by means of water circulating in thermal exchange therewith. There are a number of serious problems involved in the use of air or water for cooling the condenser. In the first place, the specific heat of air is very low and the temperature of the air is so close to the temperature of the condenser that the rate of air flow required for cooling the condenser is almost prohibitive. In order to circulate the necessary amount of air an expensive and noisy blower system would be required. The initial cost of the blower system and the cost of operating such a blower system would be high and would very materially increase the cost of operation of the air conditioning apparatus. Furthermore, it is not always convenient to supply and dispose of large quantities of condenser cooling air. Because of these facts, it has not been considered practical to use air cooled condensers except in some of the small systems. Consequently, most of the larger air conditioning units are of the water cooled type. However, with an increase in the number of water cooled air conditioning units being installed, it has been found that the average city water system and average city water disposal system is inadequate to handle the load necessitated by the water cooled air conditioning system. Many cities have now placed limitations on the use of water for air conditioning purposes. Air conditioning engineers have long known that water cooled air conditioning systems could not be used extensively for that reason and have been working for many years on the problems of providing some means for reducing the amount of air or water required by the refrigerant condensing unit. A large number of arrangements have been proposed for overcoming the problems but none have been fully satisfactory. Water cooling towers, for example, have been used but these are large, expensive and impractical for various reasons.

It is an object of this invention to provide a practical air conditioning unit in which the amount of air or water required for cooling the heat dissipating portion of the system is materially reduced.

It is well known that the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit equals one B. t. u. It is also well known that the amount of heat required to convert one pound of 212 F. water to one pound of 212 F. water vapor is 970 B. t. u. Thus, it is apparent that if it would be possible to boil the water so as to utilize the latent heat of vaporization of the condenser cooling water, each pound of F. water, for example, would provide 1,112 B. t. u. of cooling in comparison with approximately 20 B. t. u. normally made use of in 70 condenser cooling water. However, in present day refrigerating systems it is out of the question to operate the condenser at a high,

enough temperature to boil the water because of the excessive pressure differences which would be required between the high and low sides of the system.

It is an object of this invention to overcome the above difficulties by using primary and secondary mechanical refrigeration systems employing suitable refrigerants whereby the evaporator of the primary system is used for conditioning the air and the condenser of the secondary is used for boiling water or heating air to a high temperature.

Another object of this invention is to make better use of the condensate water in cooling the condenser.

A further object of this invention is to provide an improved control arrangement for an air conditioning system.

A further object of this invention is to provide a low-cost, large-capacity air conditioning system which is compact and of light weight.

One of the problems in the design and in stallation of air conditioning equipment is that of designing the air conditioning equipment so that inexperienced men can install the equipment. It is an object of this invention, therefore,

to provide an air conditioning system in which most all of the major portions of the system are assembled in proper fixed relationship before shipment from the factory.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a partly diagrammatic view showing a preferred embodiment of my invention; and

Fig. 2 is a partly diagrammatic view showing a modified form of my invention.

As shown in the drawings, reference numeral l8 designates an enclosure, the air of which is to be conditioned. The air to be conditioned is withdrawn from the room l8 through a duct l2 and is circulated in thermal exchange with a primary refrigerant evaporator l4 located in the air conditioning chamber l6. The conditioned air is returned to the room through the duct [8 in which is located a fan unit 28 which circulates the air to be conditioned in thermal exchange with the evaporator A fresh air duct 22 is provided whereby fresh air may be mixed with the air returning from the enclosure through the duct i2. The amount of fresh air flowingthrough the duct 22 may be controlled by the damper 24 arranged within the duct 22. While no controls have been shown for the damper 24, any conventional control may be provided such as the dry bulb thermostat, a wet bulb thermostat, or a combination of both, responsive either to the condition of the outside air or the condition of the return air, or to both.

The refrigerant liquefying apparatus comprises a first motor-compressor-condenser unit 26, and a second motor-compressor-condenser unit 28 both of which are mounted on a common base 28. The refrigerant vaporized in the primary evaporator I4 is withdrawn therefrom by means of the primary compressor 38 which discharges the compressed gas through the discharge port 32 leading into the motor-compartment 34 of the unit 26. The compressor 38 is adapted to be driven by means of a conventional motor 36. The compressed refrigerant discharged into the motor compartment 34, is condensed when it comes in contact with the cooling coil 38 located in the cavity 48. The condensed primary refrigerant collects in the bottom of the cavity 40 and returns to the primary evaporator through the liquid line 42. The flow of primary refrigerant to the primary evaporator I4 is controlled by means of a conventional thermostatic expansion valve 44. The valve 44 is provided with the usual thermostatic bulb 46 located adjacent the outlet of the evaporator whereby spilling over of liquid refrigerant from the evaporator l4 to the compressor 38 is prevented in accordance with well known practice.

The primary refrigerant system is charged with a low boiling point refrigerant such as dichloro-difiuoro methane. The cooling coil 38 located in the cavity 40 comprises a portion of a secondary volatile refrigerant system charged with a refrigerant having a much higher boiling point. I have found that a very suitable refrigerant for the secondary system is monofiuorotrichloro methane. The coil 38 comprises the evaporator of the secondary refrigerant system and is supplied with liquid refrigerant by the secondary refrigerant liquefying apparatus generally designated by the reference character 28. The liquid refrigerant is supplied to the secondary evaporator 38 through the liquid line 48. The flow of liquid refrigerant to the secondary evaporator 38 is controlled by a conventional thermostatic expansion valve 58 located in the liquid line 48. The thermostatic expansion valve 68 is provided with the usual form of thermostatic bulb 52 located adjacent the outlet of the secondary evaporator 38 so as to prevent liquid refrigerant spilling over from the secondary evaporator to the secondary compressor 64. The compressed secondary refrigerant discharged from the compressor 64 is discharged into the motor-compartment 66 through the discharge port 68.

The condensing temperature of the primary refrigerant is approximately F. at con'densing pressures of approximately pounds whereas the condensing temperature of the secondary refrigerant"is approximately 230 F. at condensing pressures of approximately pounds. It is apparent, therefore, that the operating pressure in each system is such that the same type of compressor may be used in each system. In order to condense the secondary refrigerant, water is supplied to the coil 68 from any suitable source 62 such as a city water main or the like. In view of the high temperatures prevailing within the secondary system, the water supplied to the coil 68 may be completely vaporized before entering the outlet line 64 whereby the high' latent heat of vaporization of the water is utilized. The construction of the refrigerant liquefying units shown is especially well adapted for a system of this type. It is apparent that the relatively cold water entering the high temperature unit 28 through the line 62 will serve to properly cool the main bearing of the compressor 54. It will also serve to cool the motor 66 which drives the compressor 54 and to subcool the secondary liquid refrigerant.

The flow of cooling water to the coil 68 may be controlled by means of a valve 68 located in the supply line 62. The valve 68 is a thermostatically controlled valve and includes a thermostatic element 10 located in thermal exchange with the water outlet 64. The calibration of the thermostat 18, is such that the valve 68 tends to close whenever the temperature of the water vapor leaving through the outlet 64 falls below a predetermined value, such as 220 F., for example. If the thermostat i8 is set so as to close the valve 68 whenever the temperature of the vapor leaving through 64 drops below 220 F., there will be approximately 8 superheat of the stem. Obviously, the values referred to throughout this description have been given for purposes of illustration only and may be varied without departing from the spirit of my invention.

The primary and secondary liquefying systems 26 and 28 are controlled by means of a thermostat 12 located within the conditioned space ill. The arrangement ofthe thermostat I2 is such that when the temperature within the conditizned space exceeds the desired space temperature, the motors 36 and 66 will be energized and w'll continue to operate under normal conditions until the temperatu e within the conditioned space reaches the desired value for which the thermostat I2 is set. It will be observed that the moto: s 36 and 66 are arranged in parallel in the electrical circuit and that a switch 88 is provided in the circuit leading to the motor 36 and a similar switch 82 is provided in the circuit of the motor 66. The switch 88 is a conventional pressure responsive switch which is operated in res onse to pressure within the chamber 34. The purpose of the switch 88, for example, is to interrupt the circuit to the motor 36 in the event of abnormal pressure conditions within the chamber 34. Thus in the event of failure of the secondary refrigerant system, the pressure within the chamber 34 would tend to increase above a safe value. This increase in pressure would automatically open the circuit through the switch 80. Similarly, any abnormal pressure within the chamber 56 would serve to interrupt the circuit to the motor 66.

In Fig. 2, I have shown a somewhat similar arrangement in which like reference characters have been used to designate like parts. In the arrangement shown in Fig. 2, the secondary refrigerant liquefying unit 28 is an air cooled unit. The unit 28 of Fig. 2, is similar to the corresponding unit shown in Fig. 1 except that heat transfer fins I and I0I have been substituted for the water coil 60. In this modification, the compressed refrigerant vapor discharged by the secondary compressor 54 is cooled by means of air circulated thereover by the fan unit I00. Inasmuch as it is desirable to introduce a certain amount of fresh air into the enclosure from time to time, it becomes necessary to remove a corresponding amount of air from the conditioned space. Inasmuch as the temperature of the conditioned air within the space I0 is considerably below the outside air temperature, especially on hot days, it is advantageous to use all of the room air which otherwise would be wasted to the outside for cooling the secondary refrigerant liquefying units 28. The fan unit I00 is arranged to circulate either fresh air from the fresh air duct IOI or room air from the duct I03. The damper I02 controls the amount of fresh air circulated. Water removed from the air by the evaporator I4 is also used to very good advantage in cooling the secondary refrigerant liquefying unit 28. A drip pan I00 is provided for collecting the condensate. The pan I08 is provided with a drain line I09 which discharges the condensate unto the unit 28 as shown. Because of the high temperature of the unit 28, the water removed from the air provides approximately 30% of the condenser cooling capacity under some conditions whereby very little air needs be circulated in com parison with the amount of air which must be circulated over the prior art arrangements.

The arrangements shown in Figs. 1 and 2 not only make more efficient use of the condenser cooling medium but also have the advantage that the complete system may be assembled at the factory and shipped as a unit to the point'of use. For purposes of illustration, the primary evaporator has been shown mounted in a remotely located air duct whereas it is within the purview of this invention to mount the entire system within a single cabinet located either within or without the conditioned space.

While the form'of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. The process of conditioning air which comprises evaporating dichloro-difluoro methane in thermal exchange with a body of air to be cooled, compressing and thereafter condensing said diehloro-difluoro methane in thermal exchange with monofluoro-trichloro methane so as to evaporate said monofiuoro-trichloro methane, compressing and thereafter condensing said monofluoro-trichloro methane in the vicinity of water at a temperature high enough to boil said water.

2 The method of conditioning air for an enclosure which comprises transferring heat from air for said enclosure into a body of refrigerant having a low boiling point, transferring said heat from said low boiling point refrigerant to a higher boiling point refrigerant and from said higher boiling point refrigerant to a body of water at a temperatrue high enough to boil said water so as to utilize the latent heat of the water for cooling said higher boiling point refrigerant.

3. Air conditioning apparatus for an enclosure comprising in combination, a, primary evaporator, means for flowing air for said enclosure in thermal exchange with said primary evaporator, primary refrigerant liquefying apparatus for supplying primary liquid refrigerant to said primary evaporator, means for cooling said primary refrigerant liquefying apparatus comprising a secondary refrigerant evaporator in thermal exchange with said primary refrigerant liquefying apparatus, secondary refrigerant liquefying apparatus for supplying secondary liquid refrigerant to said secondary evaporator, said secondary refrigerant liquefying apparatus comprising means for compressing the secondary refrigerant vaporized in said secondary evaporator, and means for condensing said secondary refrigerant including means for flowing water removed from the air by said primary evaporator in thermal exchange with 'said secondary refrigerant and means for flowing air from said enclosure in thermal exchange with said secondary refrigerant, said secondary refrigerant having a liquefication temperature considerably higher than the liquefication temperature of the primary refrigerant.

4. Air conditioning apparatus for an enclosure comprising in combination, a primary evaporator in thermal exchange with air for said enclosure, primary refrigerant liquefying mechanism for supplying primary liquid refrigerant to said primary evaporator, secondary refrigerant liquefying mechanism for cooling said primary refrigerant liquefying apparatus, means responsive to the condition of air within said enclosure simultaneou'sly controlling the operation of said primary refrigerant liquefying mechanism and said secondary refrigerant liquefying mechanism, and means responsive to the refrigerant pressure in one of said mechanisms for controlling the operation of one of said mechanisms.

5. The process of conditioning air which comprises evaporating a low boiling point refrigerant by transferring heat from a body of air to be cooled into said refrigerant, compressing and thereafter condensing said low boiling point refrigerant in thermal exchange with a higher boiling point refrigerant so as to evaporate said -higher boiling point refrigerant, compressing and thereafter condensing the higher boiling point refrigerant in thermal exchange with water at a temperature high enough to boil said water.

RICHARD E. GOULD. 

